@Martin230799 check NetworkManager is enabled
make sure this file looks like this:
phablet@ubuntu-phablet:~$ cat /etc/NetworkManager/NetworkManager.conf
[main]
plugins=ifupdown,keyfile
[ifupdown]
managed=true
[device]
wifi.scan-rand-mac-address=no
if ifupdown managed is false, networkmanager is not managing the network interfaces.
in my case it somehow works with it being false but that is most certianly some kind of bug, it should be true.